1. Field of the Invention
The present invention relates to a lead wire sealing device, and a method for sealing a housing through hole formed on a housing member.
2. Description of the Prior Art
Conventionally, in a recording disk drive such as a hard disk drive or the like, a through hole is formed on a bracket of a spindle motor and/or a housing of the recording disk drive to connect a lead wire as a part of windings of the spindle motor or the like to a printed circuit board provided in the outside of the housing or the like.
For example, forming a bracket through hole having a lead wire of the windings inserted therein on the bracket of a spindle motor, a through hole is formed on a flexible printed circuit board (hereinafter, referred to as an FPC) and the FPC through hole is located just under the bracket through hole. Further, the size of the FPC through hole is made smaller than that of the bracket through hole and whereby the FPC through hole is fit inside of the bracket through hole and when the lead wire of the windings is pulled out via the bracket through hole and the FPC through hole, the lead wire has little risk to contact directly the inner edge of the bracket through hole. The technology that the lead wire is prevented from contacting the bracket in this way omits a contact protection component such as a rubber tube or the like.
On the other hand, in the hard disk drive, the lead wire of the windings is also pulled out from a mechanism other than the spindle motor to be connected to the printed circuit board outside of the housing and the outside power source or the like. As a mechanism from which the lead wire is pulled out, a latch coil for releasing fastening of an actuator arm in a latch (fastening) mechanism of the actuator arm to which a transducer for writing the information is disclosed.
In the meantime, in the hard disk drive, by sealing the closed space of the housing having a recording disk housed therein as separated from the outside, an air around the recording disk is kept clean. Then, in order to prevent air leak to the closed space and maintain a sealed condition, the through hole for pulling out the lead wire formed on the housing is sealed by a sealing material.
On the other hand, in late years, the hard disk drive unit is also utilized in a car navigation system and high decay durability is required from a car-mounted hard disk drive. For example, in a heating and humidification test, an endurance test of 1,500 hours under temperature 90° C. and humidity 95% is done. In addition, in a heat shock test, an endurance test to repeat cooling and heating for each fifteen minutes under temperatures (−40)° C. and 85° C. alternately 1,500 times is done.
When sealing the through hole for pulling out the lead wire of the windings by one kind of adhesive, under such a severe test condition, the adhesive may have cracks or the adhesive may be separated from the housing. As a result, a gas may enter the closed space of the housing to be kept clean from outside. For example, there is a method of inserting a tubular bush made of an insulation material in the through hole and sealing the through hole after inserting the lead wire in the bush. However, such a method has a possibility that a space is left between the outer circumferential surface of the bush and the inner circumferential surface of the through hole when loading the adhesive and under the above-described high temperature, the gas in the space expands to cause cracks on the adhesive. In addition, due to a difference of a thermal expansion between the housing and the bush, a distance between the outer circumferential surface of the bush and the inner circumferential surface of the through hole may be changed upon heating and cooling and the adhesive may not follow change of the distance to be separated form the housing or the bush.